One way to predict the rate and extent of gravity displacement of fluids in a subterranean hydrocarbon reservoir is to study the behavior of the fluids in core samples obtained from the reservoir. In the laboratory, a centrifuge can be used to increase the rate of fluid replacement in core samples by substituting centrifugal force for gravity. In centrifuge experiments, core samples are saturated with oil of the type found in the reservoir, and the cores are then contacted by one or more flooding fluids while the samples are spun in a centrifuge.
As found in hydrocarbon reservoirs, oil generally contains a significant quantity of dissolved volatile components. When the oil is maintained at ambient laboratory conditions, the volatile components evaporate, leaving what is known as "dead oil". One problem encountered in simulating a process which is to occur in a reservoir containing oil with a substantial fraction of volatile components is that when core samples are saturated with dead oil, the simulation may not indicate what would happen in the reservoir. Thus, a better simulation of the displacement process is possible if the core samples are saturated with oil that contains the volatile components. This oil can be "recombined", or mixed from dead oil and volatile components equivalent to those which were previously lost. However, the saturation and displacement operations must be carried out under reservoir temperature and pressure conditions, or the volatile components will again be lost.
Thus, there is a need for a means to saturate core samples with recombined oil under reservoir temperature and pressure conditions. There is also a need for a means to maintain the core samples under reservoir temperature and pressure conditions during centrifuge studies of fluid replacement in the cores.
Accordingly, a primary object of the present invention is to provide a method for performing centrifuge studies of fluid displacement in cores under simulated reservoir overburden, temperature, and pressure conditions.
Another object of the present invention is to provide a means for performing centrifuge studies of fluid displacement in cores under simulated reservoir overburden, temperature, and pressure conditions.